#define  _CRT_SECURE_NO_WARNINGS
#include<stdio.h>

typedef struct ListNode ListNode;
struct ListNode
{
    int val;
    struct ListNode* next;
};
typedef struct ListNode ListNode;
struct ListNode* middleNode(struct ListNode* head)
{
    ListNode* slow = head;
    ListNode* fast = head;
    while (fast && fast->next)
    {
        slow = slow->next;
        fast = fast->next->next;
    }
    return slow;
}